Production of beryllium



June 21, 1938. Q KRUH 2,121,084

PRODUCTION oF BERYLLIUM Filed Aug. 29, 1935 2 sheets-sheet 1- 26 5 5 lf5 .-/j--l-lmmmmmmmmmgg f June 21, 1938. Q KRUH 2,121,084

PRODUCTION oF BERYLLIM Fil'ed Aug. 29, 1955 2 sheets-sheet 2 PatentedJune 2l, 1938 vUNITED STATES Y 2,121,084E p PRODUCTION F BERYLLIUM OsiasKruh, Vienna, Austria Application August 29, 1935, Serial No. 38,399

In Austria September 10, 1934 25 claims.

It has already been attempted to reduce beryllium oxide with the aid ofcarbon, for instance by heating, a mixture of beryllium oxide and carbonto a high temperature (of the order of 2000 C.) l0 in an electricfurnace. But the attempts made in this direction have not as yet led toany useful result, since beryllium becomes re-oxidized by the carbonmonoxide formed in the course of the reduction reaction, and alsocombines with ,carbon to yield beryllium carbide. For this reasonberyllium has been produced up to the present electrolytically. Thecommon method of practicing this manufacturing process is to electrolyzea fused mixture of BeFaNa and BeF4Ba at a temperature serve as theanode, the cathode being formed of a water-cooled iron tube. The'voltage required for this process is as high as 80 volts, and this fact,in conjunction with the low atomic Weight of beryllium, results .in acurrent consumption of 476 kilowatt-hours for the production of 1kilogramme of beryllium. 'The consumption of electrical energy is thusextremely high in comparison with the electrolytic recovery of othermetals. 30 Moreover, the production of the double salts in the requireddegree of purity is also costly, with the result that the price ofelectrolytically produced beryllium is so high as to be a bar to itsmore extensive use. I

'I'he main object of the present invention is to provide a process forthe production of beryllium which is simpler and cheaper than themethods hitherto known, and which is not dependent on the use ofchemically pure starting materials.

With the process according to the present inventicn it is possible toproduce beryllium on a L commercial scale and in a high degree ofpurity,

the essence of the process being to heat a loose mixture of berylliumoxide and carbon, preferably 5in the correct chemical proportions, to ahigh temperature, while causing a stream of inert gas, preferablyhydrogen, to flow through the charge, the heating being carried to thepoint at which the beryllium is disengaged in the form of Vapor,- forwhich purpose the charge is heated to a temperature of at least 1900 C..The hydrogen surrounds the evolved beryllium vapor and protects 'itfrom reaction with carbon monoxide and carbon, so that both there-formation of beryllium 55 oxide and the formation of berylliumcarbide are avoided. The gaseous and vaporous mixture is.

conducted continuously out of the reaction chamber, and immediatelycooleddown to such an extent that no reaction at all can take place be-60 tween theberyllium on the one hand and the of 1350 C. in an AchesonCrucible connected to (Cl. 'I5-84) gaseous reaction products and carbonon the other hand. A major portion of the beryllium becomes depositedfrom the vaporous phase on to the cooled surface of the chilling deviceemployed, while the gases are drawn off together With the remainder ofthe beryllium. The deposited beryllium can be detached from the coolingsurfaces by mechanical means, and conveyed into a collecting chamber.The portion of the beryllium which is not deposited is carried alongwith the protective gas, which also contains carbon monoxide, and canthen be separated out vfrom the gases in any suitable manner, seeingthat it in part becomes deposited in the further course ofv its traveland in part can be recovered by mechanical or electrical filtration.

In practicing the process of the present invention it is advisable tomake the reaction chamber of trough shape and to provide immediatelyabove this reaction chamber a cooling device which may consist forexample of a rotary drum extending over the entire length of thereaction chamber and cooled internally, so that the beryllium vaporrising from the reaction mixture becomes deposited on the peripheralsurface thereof. The beryllium is deposited on this surface in a finelydivided state, and can be removedtherefrom by means of a scraper andremoved from the furnace by means of any suitable conveying device.

The heating of the reaction chamber is best effect-ed electrically, andthat preferably by means of alternating current.

It has been already mentioned above'that hydrogen is preferably used asprotective gas, the reason being that beryllium is more readily volatilein a current of hydrogen. At the high furnace temperature used,considerable quantities of acetylene are formed by the action of thehydrogen on the carbon contained in the reaction mixture, which takesplace at the expense of the heating energy supplied, since the reactioninvolved is endothermal. This does not, however, imply any loss ofenergy, since, as is Well known, acetylene exerts a powerful reducingaction, and the assistance rendered by the acetylene in effecting thereduction of the'beryllium oxide is equivalent to recovery of the energyabsorbed.

If acetylene be consumed in the reaction there results a disturbance ofthe temperature equilibrium between hydrogen, carbon, and acetylene,with the result that acetylene is again at once formed, the hydrogengenerated on the splitting of acetylene combining once more with carbonto l Moreover, the fact that the ployed jointly for the purpose of thereduction in question.

The formation `ofpure beryllium can also be aided by a furtherexpedient. This expedient consists in sintering berylliumoxide,comminuting it to about pea-size, `and mixing it with carbon of aboutthe same size. The result achieved in this manner is that the reductiontakes place on the surface of the particles of beryllium oxide, thusrendering the velocity of the reaction uni- Y form. The berylliumdisengaged at any moment in the form of vapor at the surface of the`oxide particles is at once surrounded by the protective gas, so thatcarbide formationv is precluded while at the same time, since theevolution of vapor takes place uniformly, the various measures andphases of the process, that is to say the vsupply of hydrogen, thedeposition of the metal vapor, the detachment of the deposited metalfrom the cooling device, and the like, can also be caused to proceeduniformly, that is to say at a uniform rate.

The quantity of protective gas employed in the carrying out of theprocess need by no means be large. In consequence of the low molecularweight of hydrogen, the average velocity of the hydrogen particles isconsiderably higher than that of carbon monoxider or that of berylliumvapor, or that of carbon vapor. Hydrogen thus occupies more space thancarbon monoxide and carbon vapor, and an amount of hydrogen about 3-4'times that of the carbon monoxide present is suflicient to protect theparticles of beryllium. In order tokeep the charge at an eventemperature it is advisable to pre-heat the protective gas outside thefurnace.

The following example may serve to illustrate the nature of thereaction. vAssuming the furnace to be operated uninterruptedly, thereaction proceeds on the following lines:

2800 g. BeO-l-1350 g. C|990 g. Hz:

' 1000g. Be+3150 g. CO+990 g. H2

Analyses of the product show beryllium yields of 98-99.5%, the remainderbeing beryllium oxide.

A constructional example of apparatus for the carrying out of theprocess according to the invention is shown in the accompanyingdrawings, in which:

Fig. 1 is a side elevation of the plant, partly in section taken on theline A-A of Fig. 2.

Fig. 2 is a front elevation partly in section taken on the line B-B ofFig. 1. y

Fig. 3 is a plan view partly in section taken on the line C-C of Fig. 1.

In" the furnace .I there is provided an elongated shallow trough 1 whichserves as a reaction chamber for the production of beryllium byreduction. The walls of this chamber are provided with a lining 2 ofrefractory material, protected from the action of excessive temperatureby the cooling tubes 8f. I

The reaction chamber 1 communicates through a channel 6 with the topportion 3 of the furnace, this top'portion being provided with a rotarysieve 4 and, lower down, with a gas inlet 5. In rder to carry out theprocess of reducing beryllium oxide according to the invention the,v'reaction chamber 1 is filled with this Oxide together with thereducing agent, and with the protective gas. For example, a mixture ofberyllium oxide and carbon, in the correct proportions is supplied tothe chamber 1 through the top -portion 3 of the furnace and the channelE, the sieve 4 being rotated at the speed required to maintain a balancebetween the rate of feed of the material to thereaction chamber and therate at which the products of reaction leave the same; at the same time,hydrogen enters at 5, and is introduced into the reaction chamberthrough the temperature, and in the presence ofhydrogen the reduction ofthe beryllium oxide to metallic beryllium takes place.

The protective gas flows through the reaction chamber and carries thereaction gases, consisting mainly of carbon monoxide, together with theberyllium vapor towards an internally cooled.

rotary cylinder II located above and longitudinally of the reactionchamber. This gaseous mixture is cooled by the cylinder II to a temableto oxidize beryllium. The beryllium vapor is deposited on t e surface ofthe cooled'cylinder in the form of kind of metallic snow, and is `thenscraped 01T this cylinder by means of a movable scraper I2, and conveyedthrough the funnel-shaped chute I3 into a cylindrical channel I8 whenceit is carried by a conveyor helix I4 through the discharge pipe I9 tothe chamber I5 whereit collects. The portion of the beryllium notdeposited on the cooling surface but carried on by the flowing gasmixture settles on the conveyor helix I 4, and the last traces ofberyllium are retained by the mechanical filter I6 or an electric filterin the chamber I5. A block-shaped packing 20 interposed between the topof the cylinder II'and the inner wall of the furnace I prevents the flowof hydrogen from by-passing the reaction chamber 1.

The mixture of hydrogen and carbon monoxide leaves the chamber I5 at I1,and may be used, subsequently, for any desired purpose. I'prefer,however, to recover the pure hydrogen from this mixture and tore-conduct it into the furnace I in order to obtain in the apparatus aclosed circulation of the protective gas. To this end, as shown in Fig.1 by the chain-dotted lines, the mixture of gases is passed from thechamber I5 through the conduit 2| to a device 22 in which the hydrogenis separated from the carbon monoxide and from other impurities, andreturned to the furnace through the conduit 23, a pump or exhauster24.01 conventional design being interposed in this conduit' for thepurpose of maintaining the required circulation of the hydrogen. Freshhydrogen may be supplied to the furnace or may be fed ,into circulationby the pipe 25 or by the pipe 26. Means for separating .pure hydrogenfrom a gaseous mixture containing hydrogen are well known in the art,and their special construction does not constitute any part of myinvention. Thus, by the' rectangle 22 I have only indicated where such adevice could be placed, Without showing the known parts of this device.

The finely divided beryllium collecting in the chamber. I5 may be usedin this state for chem- `ical or other purposes. It may also be castinto Aperature at which carbon monoxide is no longer bars or ingots, andused for any purpose for which beryllium is manufactured.

Preferably, the casting process may be carried out at once in thecollecting chamber I5 so that it takes place in the presence and underthe protective action of the protective gas (e. g. hydrogen) used in thereduction process. For this purpose, the chamber I5 may be constructedin any known manner, but preferably in the manner shown by way ofexample in Fig. 1. In this iigure the inner Walls of the chamber I5 arecovered with a lining 21 consisting of a refractory material which doesnot react with molten beryllium, for instance cryolite, magnesite, orany other suitable brick, but I'prefer to use sintered aluminium oxideor beryllium oxide, since this lining material gives excellent results.The beryllium collecting in lthe chamber I5 is melted upon a casting bedwhich is constructed in the manner of a filter, comprising a. perforatedbotton 28 carrying a heaped layer 29 of a refractory material incapableof reacting with beryllium at elevated temperatures. This material maybe the same as that of the 1ining'2l, for instance cryolite, magnesite,or the like, but pref- \erably sintered alumina. To melt the berylliumany suitable heating means may be provided, and

preferably electrical means, for example a high frequency coil 30disposed outside the chamber I5, as shown in Fig. 1. The construction ofelectrical heaters for melting and casting vpurposes is well known inthe art and, therefore, does not constitute any part of my invention.The molten beryllium passes into the bottom part of the chamber I5through the filter 28, 29 which retains any impurities, and may then bedischarged from the chamber I5 through the :outlet provided thereon.

The apparatus is to be considered as fitted with the requisite coolingand driving instrumentalitiesfit being understood that I do not claimthe particular construction of such instrumentalities, since the sameare frequently used inmetallurgical and electro-metallurgical processes,and are known per se. In the apparatus shown in the drawings thecylinder Il, the tubes 3, and the electrodes I0 are water-cooled duringthe operation of the plant.. For this purpose water inlet pipes 32, 34,36, and water outlet pipes 33, 35, 31 are provided. The pipe 32 extendsinto theinterior of. the cylinder II so as to discharge cooling waterinto the same. The Water leaving the cylinder Il through the spout 38ows into the vessel 39, and thence into the pipe 33. 'Ihe ends ofthecooling tubes 8 are fitted into water distributing chambers 40 and 4I,these chambers being connected to the pipes 34 and 35, respectively, soas to allow the cooling water to flow from 34 through 40, 8, and 4I into35. Each electrode I0 is partly surrounded by a water-filled casing 42which is connected on one side to the inlet pipe 3B and on the other tothe outlet pipe 3,1.

The axles 43, 44, and 45 of the sieve 4, cylinder II, and conveyor I8are lrotatable in bearings 46, 41, and 48, respectively, and are fittedwith pulleys 49, for rotation therewith at the required speed. Thecylinder II is driven by a pulley 5I secured to the tube 38. It will beclear that the pulleys 49, 50, and 5I may be replaced by any `othersuitable transmission or driving means, for instance for electric drive.

The top 3 of the furnace I may be closed by a cover 52 pivoted at 53 andhaving handles 54.

When electric resistance heating is employed in the furnace, thedescribed process does not even require $430 part of the electricalenergy required for carrying out the hitherto usually practicedelectrolytic method of manufacture. It is also not necessary with thepresent process to produce the complex double salts necessary for theelectrolytic process. A further advantage of the process according tothe present invention over the electrolytic process resides in the factthat alternating current can be employed, implying considerably lowerinstallation costs as compared with direct current. If sufficiently purecarbon ,or acetylene be employed in the presence of hydrogen for thepurpose of the reduction, highly refined beryllium is obtained, sincethis metal sublimes in a current of hydrogen. After sublimation, theberyllium becomes deposited yin the form of fine crystals.

In consequence of its low atomic weight, beryllium is used for a varietyof purposes. Thus for example it is very Well suited as material forthev outlet windows for the electrons in electric discharge tubes. Afurther use for beryllium is in the production of alloys with manyYother metals. When added as an alloying constituent to aluminium itincreases the strength of the latter. An alloy of aluminium, copper, andberyllium exhibits particularly valuable properties, for instance.

To produce an alloy ofA aluminium and beryllium it is not-necessary, inthe recovering of these metals, to separate the beryllium oxide from thealuminium oxide, since aluminium and beryllium have the same boilingpoint, so that these metals can be reduced simultaneously by the abovedescribed process in one and the same furnace. In this manner there isobtained a high percentage aluminium-beryllium `alloy which can be addedto aluminium or its alloys.

When beryllium ore is employed which contains silica in addition toaluminium oxide the silica can be slagged for example by the additionofiron, whereupon the slag formed flows out of the furnace. TheA12O3.3Be0 left behind is then subjected to the process described above,with the result that an aluminium-beryllium alloy is obtained in asimple and inexpensive manner.

I claim:

1. In the manufacture of beryllium or beryllium alloys, the processwhich comprises reducing beryllium oxide with the aid of carbonaceousmaterial in the presence of a protective gas which is inert to berylliumat a temperature sufficient to vaporize into said gas the berylliumformed by reduction.

2. In the manufacture of beryllium or beryllium alloys, the processwhich comprises preparing a mixture containing beryllium oxide andcarbonaceous material exposing lsaid mixture to the action of a flowingprotective gas inert to beryllium while heating the mixture to atemperature suincient to reduce beryllium oxide by the action of thecarbonaceous material and to vaporize into said protective gas theberyllium formed by reduction; carrying away the composite of metallicvapour, protective gas, and gaseous reaction products formed during th-esaid reduction process; and cooling said composite to a gaseous reactionproducts formed during the said reduction process; and cooling saidcomposite to a temperature sufficiently low 4to prevent the berylliumparticles from reacting with the said gaseous reaction. products and tocondense the beryllium vapours so as to obtain the beryllium in thesolid state. v

5. In the manufacture of beryllium, the process which comprises looselymixing beryllium oxide and carbon; heating said mixture to a temperaturesufcient to reduce said xide by the action of the carbon and to vaporizethe beryllium formed thereby; surrounding the vaporized berylliumparticles with a protective gas inert to beryllium so as to protect saidparticles from the chemical attack by other gases present; carrying awaythe gaseous mixture of beryllium vapor, protective gas, and reactiongases formed during the reduction process; cooling said gaseous mixtureto a temperature suflicient for preventing the beryllium particles frombeing oxidized by the said reaction gases; and removing from the saidgaseous mixture the beryllium in the solid state.

6. The process, as claimed in claim 2, wherein the beryllium oxide andthe carbonaceous material are contained in the said mixtureinproportions corresponding substantially to the stoichiometricalrelation between beryllium oxide and carbon.

7. In the manufacture. of beryllium or beryllium alloys, the processwhich comprises reducing beryllium oxide with the aid of carbon hydridesin the presence of a protective -gas inert to beryllium at a temperaturesufilcient to vaporize into said gas the beryllium formed by reduction.

8.` In the manufacture of beryllium or beryllium alloys, the processwhich comprises reducing beryllium oxide by acetylene in the presence ofhydrogen at a temperature sufficient for vaporizing into said hydrogenthe beryllium' formed by reduction.

9. In the manufacture of beryllium o'r beryllium alloys',l the processwhich comprises reducing beryllium oxide with the aid of a carbonaceousmaterial in the presence of a gas mixture containing hydrogen and atleast one hydride of carbon, said reducing process being carried out ata temperature sufficient for vaporizing into said gas mixture theberyllium formed by reduction.

10. In the manufacture of beryllium or beryllium alloys, the processwhich comprises reducing beryllium oxide with the aid of a carbonaceousvmaterial in the presence of a gas mixture containing hydrogen andacetylene, said reducing process being carried out 'at a temperaturesutiltained in a proportion which is sufllcient to protect the berylliumparticles from the attack by other gases present and to prevent theforma-` tion of beryllium' carbide.

12. In the manufacture of beryllium, the process which comprisesreducing beryllium oxide with the aid of carbonaceous material in thepresn ence of iiowing hydrogen at a temperature suillcient to vaporizeinto said hydrogen the beryllium formed by reduction, the amount ofhydrogen supplied to the process being at least three times that of thecarbon monoxide formed by the restantially to the temperatureequilibrium between hydrogen, carbon and acetylene, said reducingprocess being carried out at a temperature which is sufficientlyelevated for vaporizing into said gas mixture thev beryllium formed byreduction.

14. The process of manufacturing beryllium,

4which comprises heating a mixture of beryllium oxide and carbonaceousmaterialin a reaction chamber to a temperature which affords thereduction of the beryllium oxide by carbon and the vaporization of theberyllium formed thereby; supplying to said ehamberla protective gasinert to beryllium; withdrawing from the reaction chamber., the mixtureof beryllium vapour, protective gas, and gaseous reaction productsformed during the said reduction process cooling said mixture whenleaving the reaction chamber, to a temperature sufficient to preventoxidation of the beryllium and formation of beryllium carbide and tocondense the beryllium vapour; carrying away the condensate of berylliumfrom the reaction chamber together with the said gaseous mixture; andseparating froml this i latter the beryllium in the solid state.

15. In the manufacture of beryllium or beryllium alloys, the processwhich comprises heating a mixture containing beryllium 'oxide andcarchamber to a temperature suiiicient to condense the metallic vapour;collecting the metallic particles condensed; recovering the saidprotective glas in a pure state'from the said composite; and repassingthe recovered protective gas. through the reaction chamber.

16. The process of manufacturing beryllium, which comprises reducingberyllium with the aid ofcarbonaceous material in the presence of aflowing protective gas inert to beryllium at a temperature suiiicientfor vaporizing into4 said gas the beryllium formed by reduction;carrying away and cooling the mixture of gases and vapours formed duringthe said reduction process;

state; collecting'the beryllium condensed; heating the berylliumcollected to a temperature sufficient for fusing the same, and castingthe fused beryllium.

17..The process. of manufacturing beryllium as set forth in claim 5characterized in that the beryllium oxide to be reduced is used in asintered state and in the shape of particles of condensing the berylliumvapours from the said mixture so as to obtain beryllium in the solidabout pea-size and that the carbon as reducing agent is also used inparticles of about pea-size.

18. In the manufacture of alloys of beryllium with aluminium, theprocess which comprises preparing a mixture containing aluminium oxide,beryllium oxide and a carbonaceous material; exposing said mixture to aflowing protective gas inert to aluminium and beryllium while heatingthe mixture to a temperature sufcient to reduce the beryllium oxideandthe aluminium oxide by the action of the carbonaceous material and tovaporize into said protective gas the aluminium and the beryllium formedby reduction; carrying away the composite of aluminium vapour, berylliumvapour, protective gas and gaseous products formed during the saidreduction process; and cooling said composite to a temperaturesuiilcient to transform the aluminium vapour and the beryllium vapourinto the solid state and to prevent the particles of aluminium andberyllium'from reacting` with the said gaseous reaction products.

19. The process as set forth in claim 18, in which the said mixture isprepared of ores containing silica in addition to the beryllium oxideand the aluminium oxide, and of a substance adapted to form with thesilica a slag, which flows out of the reaction chamber.

20. In the manufacture of beryllium, the process which comprisespreparing a loose mixture of beryllium oxide and carbonaceous reducingmaterial so that gas brought into contact with said mixture has accessto the inner particles thereof;.exposing said mixture to a flowingprotective gas inert to beryllium while heating the mixture to atemperature suillcient to reduce affords the reduction lof both oxidesby carbon and the vaporization of the beryllium and aluminium formedthereby; supplying to said chamber a protective gas inert to berylliumas well as to aluminium; withdrawing from the reaction chamber thecomposite of beryllium vapor, aluminium vapor, protective gas, andgaseous reaction products formed during the said reduction process,cooling said composite when leaving the reaction chamber to atemperature suiiicient to condense the beryllium vapor and the aluminiumAv apor and to prevent the formation of beryllium carbide and aluminiumcarbide; carrying away the condensate from the reaction chamber togetherwith the said gaseous composite; and lseparating from this latter aberyllium-aluminium alloy in the solid state.

23. In the manufacture of beryllium alloys, the process which comprisesheating a loosemixture containing beryllium oxide and carbonaceousmaterial in a reaction chamber to a temperature which affords reductionof the beryllium oxide by carbon and vaporization of the berylliumformed thereby; supplying to said chamber a protective gas inert toberyllium; withdrawing from the reaction chamber the composite ofberyllium vapor, protective gas, and gaseous reaction products formedduring the said reduction process; cooling said mixture immediatelyafter leaving the reactionchamber to a temperaturesufiicient to preventoxidation of the beryllium an formation of beryllium carbide and tocondense the beryllium vapor; carrying away the condensate from thereaction chamber together with the said protective gas, and gaseousreaction products formed during the said reduction process and coolingsaid composite to a'. temperature suincient to transform the berylliumvapor-ized into the solidstate and to prevent the beryllium particlesfrom reactingwith the said gaseous reaction products.

21. In the manufacture of beryllium-aluminium alloys, the process whichcomprises preparing a loose mixture containing beryllium oxide,aluminium oxide and carbonaceous reducing material so that gas broughtinto contact with said mixture has access to the inner particlesthereof; exposing said mixture to a ilowing protective gas inert toberyllium as well as to aluminium while heating the mixture to atempera- 'ture su'filcient to reduce both, the beryllium oxide and thealuminium oxide, by the action of the carbonaceous material and tovaporize into said protective gas the beryllium and aluminium formed byreduction; carrying away the composite oi' beryllium vapor, aluminiumvapor, protective gas, and gaseous reaction products formed during thesaid reduction process; andcooling said composite to a'temperaturesumcient to condense from the said vapors a beryllium-aluminium alloyandto prevent said alloy from reacting with the said gaseous reactionproducts.

22. The process of manufacturing alloys of beryllium with aluminium,which comprises heating in a reaction .chamber a loose mixturecontaining beryllium oxide, aluminium oxide and carbonaceous material toa temperature which gaseous mixture; andseparating from this latter thesaid condensate in the solid state.

24. In the manufacture of beryllium or beryllium-alloys, the processwhich vcomprises preparing a loose mixture containing pea-sizedparticles of carbon and of sintered beryllium oxide ;-heat ing saidmixture to a temperature suilicient to reduce said oxide by the actionof the carbon and to vaporize the beryllium formed thereby; and at thesame time exposing said mixture to a flowing protective gas inert toberyllium so as to protect the beryllium from the chemical attack byother gases present; carrying away the gaseous composite of berylliumvapor, protective gas, and gaseous reaction products formed during 'thesaid reduction process; and cooling said composite to a temperaturesuiilcient to prevent the beryllium particles from reacting with thesaid gaseous reactionproducts.

25. In the manufacture of alloys of beryllium with aluminium, theprocess which comprises preparing a mixture containing beryllium oxide,aluminium oxide and a carbonaceous material; exposing said mixture toilowing hydrogen while heating the mixture to a temperature suiilcientto reduce both oxides by the action of the carbonaceous material and tovaporize the aluminium.

